Alkylations of benzene and other similar aromatic streams yield a polyphenylated alkane by-product. Quanities of polyphenylated alkane are collected in the bottoms part of the commerical process after the desired linear alkyl benzene is separated by distillation. Certain color causing compounds are typically contained in this polyphenylated alkane, and since no satisfactory commercial method exists for the removal of these color causing compounds, the commerical use of the polyphenylated alkane by-product is severely limited. If a satisfactory commercial method existed for the removal of the color causing compounds from polyphenylated alkane, the value and utility of this material would be enhanced. For example, it would be possible to use the clear polyphenylated alkane as a secondary plasticizer.
A variety of methods are found in the art which teach the de-colorization, of aromatic hydrocarbon streams. U.S. Pat. No. 3,729,522 teaches the preparation of low color polyphenyls which are by-products of pyrolysis. The color is removed by contact with alkali metal at a temperature of 225.degree. C. for a sufficient amount of time. The polyphenyls can then be used as a plasticizer. U.S. Pat. No. 3,363,020 teaches the de-colorization of biphenyls by adding sulfuric acid and then distilling.
Another less pertinent method relates to purification and is disclosed in U.S. Pat. No. 2,932,677 teaching the removal color precursors from an already clear cut of alkyl aryl hydrocarbons. This process is keyed to removing color precursor compounds which are described as polynuclear hydrocarbon characterized by blue fluorescence, and which cause impure colored sulfonation product when clear, detergent quality alkyl aryl hydrocarbon was sulfonated. These color precursor bodies were removed through an oxidation treatment, followed by phase separation, followed by acid treatment and another phase separation. At this point, the patent describes the alkyl aryl hydrocarbon stream as being substantially clear. A clay treatment is then used at the termination of this process to remove the acid traces which still remain in the stream.
Another method teaching the removal of colored impurities is found in U.S. Pat. No. 3,835,037 which describes the removal of color bodies from mixed hydrocarbon feedstock containg napthlene by contacting with clay to polymerize the impurities. Distillation always follows this clay treatment to separate polymerized impurities.
The methods thus far described relate to the purification of compounds which are merely similar to the polyphenylated alkane of the instant invention. It would be beneficial to provide a cheap, simple method to remove color causing compounds which are found in the polyphenylated alkane by-product stream from alkylation reactions.